Compressor rotors of gas turbine engines, such as the fan of a turbofan for example, may experience two main types of aerodynamic instability: stall flutter and supersonic flutter, as shown in FIG. 6.
Supersonic flutter (which can be either stalled or unstalled, as shown in FIG. 6) occurs in the high speed regime of the compressor where tip speed is very high. Supersonic flutter can cause an operational barrier which makes it difficult to simply accelerate through a speed range in order to avoid and/or limit the effects of supersonic flutter once it occurs. Supersonic flutter may occur under certain flight conditions. Prolonged operation of a compressor rotor undergoing supersonic flutter can produce a potentially undesirable result, such as airfoil stress load levels exceeding threshold values and/or resonant stresses.
Improvement is therefore sought.